Tuning structure for radio sets



Nov. 20, 1945. s. s. CRAMER 2,339,487

TUNING STRUCTURE FOR RADIO SETS Filed bee. 50, 1943 3 SheetsSheet 1 iiiiiiifi'i'ii u f E Nov. 20, 1945. s. s. CRAMER TUNING STRUCTURE FOR RADIO SETS F iled Dec. 30, 1945 s Sheets-Sheet 2 WW W1 HIIMQ mi if INVENTOR ,24 flfifi ATTORNEY NW. 2% 1945. s. s. CRAMER TUNING STRUCTURE FOR RADIO SETS I Filed Dec. 30, 1945 3 Sheets-Sheet 3 ZSmaentor utiomcg Patented Nov. 20, 1945 UNITED STATES PATENT OFFICE TUNING STRUCTURE FOR RADIO SETS Stanley S. Cramer, Haddon Heights, N. J. Application December 30, 1943, Serial No. 516,263

28 Claims. (Cl. 25040) This invention relates to a tuning structure for use in connection with radio receiving sets and is particularly adapted for sets that are operated at a distance, such sets usually being referred to as of the remote control type. However, the invention is not limited to remote control as the apparatus to be hereinafter described may be operated from push buttons mounted directly on the radio set. I

It is one Of the objects of my present invention to provide a tuning structure in which accuracy of tuning is the salient feature.

Another object of my invention is to provide a construction in which the tuning is done very quickly and precisely by electro-mechanical means, thereby eliminating many of the personal difficulties encountered in tuning in various radio stations.

A further object of m invention is to provide a tuning system wherein means are provided for eliminating 'all noise from the loud speaker when shifting from one station to another.

Other objects will no doubt be apparent to one skilled in this art after reading the following specification taken in connection with the annexed drawings, wherein:

Figure 1 is a plan view of one form of my invention, with the tuning member, which is illustrated as a condenser with the rotor and its operating means, in the all-out or zero tuning position,

Figure 2 is a. side elevation of Figure 1, looking in the direction of the arrows 22, but with the rotor and its operating means in the all-in or full capacity position.

Figure 3 is a view of Figure 2, looking from left to right, with one of the control units removed from the unit.

Figure 3a is a fragmentary view of one of the frame support members which assists in carrying the units.

Figure 3b is a corresponding view looking at the other frame support part for the units of Figure 3.

Figure 3c is a side view of a modified form of control unit.

Figure 4 is a side elevation of the detached control member of Figure 3 looking from the reverse side, and with the member in upright position.

Figure 5 is a section approximately on the line 5-5 of Figure 2, some of the parts being shown in elevation and with certain of the parts shown in tuning position.

Figure -6 is a partial view of a complete radio set showing the tuning apparatus differently arranged from that of Figures 1 to 5 inclusive.

Figure 6a is a view of the arm which operates the positioning member of Figures 6 and 7, together with other parts.

Figure '7 is a plan view looking down on the top of Figure .6, some of the set parts being eliminated.

Figure 8 is a diagrammatic circuit arrangement of the apparatus shown in Figures 1 to 5 inclusive. 7

Figure 9 is a partial wiring diagram of the arrangement shown in Figures 6 and 7.

In the various views, wherein like numbers refer to corresponding parts, I is a framework which supports a condenser structure 2. As 11- lustrated particularly in Figures 2, 3 and 5, the condenser structure comprises two tuning units composed of stators 3 and 4 with their respective rotors 5 and 6. As illustrated, the condenser structure 2 comprises a unit which is mounted within the framework I, although it is to be distinctly understood that the stator and rotor units may be mounted directly in the framework l. The rotors 5 and 6 are carried on a rotor shaft 1 which preferably projects through the frame, and on this shaft is mounted the armature 8 of a solenoid type'of electromagnet, the field structure of which is indicated at 9, and the winding or coil at H]. The armature 8 is circular in form and has a rotary movement of at least degrees so that it is capable of directly rotating a, tuning condenser whose rotor requires to be turned 180 degrees from full-in to full-out position. 7

The solenoid structure is carried on the framework by any suitable means such as studs If and 12. A spring l3 has one end fastened to the stud l4, while the other end is connected to the shaft 1. The spring [3 serves to move the rotor or rotors, together with the armature 8, back toward normal or all-in or full tuning position after it has been moved in the manner which will be hereinafter described.

The shaft 1 carries a gear l5 which is in mesh with a toothed segment [6 that is pivoted intermediate its ends to the condenser structure 2 or the frame I whenthe condenser unit is built directly into the framework I. To the end of the segment opposite the gear teeth, is attached a rod H which carries, near its opposite end, an arm I8 pivoted at l9 to the condenser structure or the framework. It may be mentioned at this point that the rod I1 is referred to in the claims as a positioning member since it is connected in the manner just described to the rotor shaft and thereby serves to determine the position of the rotor in a manner to be later described.

Carried by the framework I and in the orifices of the frame parts la and lb, shown in Figures 3a and 3b, are a plurality of slidable members, one of which is shown in Figure 3 as detached from the frame and in turned-over position. Each of these members is composed of a slide 20 made up of suitable relativel thin strip material, preferably of steel. The slide 20 has aportion out out forming two projecting arms 2| and 22 which engage upper and lower portions of the slot 23 in the frame part |b. The slide 28 also has an arm or finger 24 projecting toward the arms 2| and 22, and the finger 24 engages a notch 25 in the upper part of the frame part la, while the lower edge of the slide 20 enga es a similar notch 25 in the bottom part of the frame portion la. The arms 2|, 22 and 24 have considenable resilience so that when the slide 20 is pushed into place into the frame parts la and lb, all wobble, especially in the direction at right angles to the slide 20, is eliminated.

When the metal between the arms 2| and 22 is punched out, a lug 26 is thrown outwardly from one side of the slide 2|]. This lug is tapped to receive a screw 21, the head 28 of which engages the exterior surface of the frame portion 29, preferably turned upwardly from the base of the frame.

Carried on the screw 21 is a spring 30 which is positioned between the lug 2B and the frame portion 29. This frame portion is utilized to take up all lost motion or slack in the screw connection with the slide 20. Pivoted to the slide 20 at 3|, is a stop member 32. The stop member 32 has a pin 33 with an enlarged head on the side of the slide 2|] as shown in Figure 4. The pin 33 operates in a slot 34 of the slide 20 and thus acts as a guide for the stop member 32. As shown in Figure 4, the outer end of the arm 24 is beveled in order to provide room for assembly of the stop 32 with the pin 33 fastened thereto.

The outer extremity of the stop member 32 may be made in the forms shown in Figures 3 and 30. In Figure 3, the surface 35 is formed on a radius from the pivot point 3|. This surface cooperates with the curved surface of the circular rod or positioning member I1, whereby when the member |1 comes in contact with this surface 35, the pressure caused by the returning spring or mechanism of the rotor and positioning member is sufficient to hold the stop lever 32 in its set position, even though its stop magnet 4| is deenergized.

In Figure 3c, the surface 35 is defined by a curve e to f which preferably has the same radius as the positioning member l1, while from f to g the surface is substantially straight. The reason for this construction is to insure that the stop lever is moved sufficiently when engaged by the rod |1, so as to break the attraction between the end of the core 3| of the magnet 4| and the portion 45' of the stop lever 32, caused by the residual magnetism. As a matter of fact, I have found that because of the substantially closed magnetic field of this construction, the residual magnetism is sufficient to hold the lever 32 in stop position even after a relatively long period of time; and when hit by the rod IT on its return movement, the magnetic field is broken down so that when another tuning slide is operated, the lever 32, previously operated, will return to normal position when the rod I1 is moved away from it; but, as stated, to insure absolute action, I prefer the construction shown wherein the rod H, on its return movement, strikes the straight surface fg which will move the lever 32 downwardly away from the magnet core 8| and then slide into the positive seat formed by the curved surface e,f.

A spring 36 carried by the stop member 32 has its free end in contact with a pin 31 on the slide 20 for returning the stop lever 32 to its normal position after being released from its stop position as will be hereinafter described. The stop lever 32 has a projection 38 which is adapted to contact with a resilient member 39 of any suitable material carried on the end of an insulator 48. The purpose of this particular construction will be later explained. On the insulator 40 is positioned an electromagnet 4|, the winding of which is adapted to be connected as by a pair of leads 42 and 43 with terminals on a connecting rack 44 that is carried by the frame. To avoid confusion, only one pair of these leads is indicated as being connected to the disassembled slidable member in Figure 3, but it is to be un derstood that when the electromagnet 4| is energized, it attracts the portion 45 of the stop lever 32 and will move it into the position shown in Figures 3 and 5.

In Figure 30 there is shown a modified form of slidable control member wherein the member 20 has an upright arm terminating in a downwardly extending portion 8| carrying the winding 4|. The stop lever 32 has a portion 45 located adjacent the end of the portion 8 to be attracted thereby. A spring 36 is supported by lugs 82 and 83 on the stop member 32 and slide 20 respectively. This construction provides a nearly closed magnetic circuit and is more efficient electrically than the construction previously described.

As shown in Figures 2 to 5 inclusive, a supplemental electromagnet 45 is mounted on an insulator 41 that in turn is fastened to a frame support member 48. The support member carries another insulator 49 on which is mounted a movable spring contact member 50 and a stationary contact member 5| that has contact, normally in electrical connection, with the spring 50. The insulator 49 also carries another contact 52 which is engaged by the contact on the spring 50 when this is moved downwardly by a bar 53 of insulating material. The bar 53 is pivoted at 54 to the frame and has its free end projecting over the free end of the spring 5|].

On the outer extremity of the spring 50 is carried a piece 55 which may be termed an armature that is of magnetic material so that when the portion 56 of the armature is moved by the lever 53, downwardly into engagement with the end 51 of the adjustable core of the electromagnet 46, the armature 55 and the spring 50 will be held in this position for a purpose to be hereinafter referred to. In this particular construction of Figures 1 to 5, the electromagnet 46, as shown, is designed particularly for operation with direct current. However, it may be constructed to operate with alternating current, the same as the solenoid structure heretofore described.

In Figures 6, 6a and '1, which were made from a radio receiving set, the slidable members 20 with their stop levers and stop magnets are of substantially the same construction as heretofore described with respect to Figure 3, but they are mounted in a difierent manner with respect to the tuning mechanism which, as shown, is alsoa gang condenser, for, as will be seen, these siidable members are mountedabove the condensers 9! in Figures 6 and "I, while in Figures 1 to '5 they are mounted below the condenser; and, correspondingly, the positioning rod or member I! is located above the condenser instead of below.

In Figures 6 and 7, the same type/of solenoid construction is used, the armature 8 thereof be ing connected to the rotor shaft directly and through a. similar gear or pinion 1'5 with a toothed segment or rocker arm 16 having a forked end '11 for receiving the positioning member I 1. Both ends of the positioning member I! are supported in a similar manner. Incidentally, it may be mentioned that 59 is a dial wheel for the radio set which is driven by the gears 60 and 6|, the latter of which is operatively connected to the shaft of the solenoid armature 8. The shaft 62 is adapted to carry a manual control knob or handle. The reel 63 and associated parts, including the pulley '58, are used in connection with the manual control of any entire slide unit;

for example, the slide 18 which may be manually moved or tuned to any desired position.

In Figure 6a, which is taken from the lefthand end of Figures 6 and 7, I have shown in substantially full size, a rocker arm 16 which is pivoted by a pivot pin- 84 to a frame member. The same pivot pin 84 acts as a pivot for an auxiliary arm 85 which has a lug 86 carrying a screw contact 81 adapted to engage a spring contact member 88 supported on an insulator 89 carriediby. the arm 15. It is to be understood, as heretofore pointed out, that both ends of the condenser have similar rocker "arms 16 and auxiliary arms '85, and the upper ends of these auxiliary arms carry the positioning member "IIthat is located in the space 11 between the two forks c and d of the arm 18. fThe width of the space 11' is sufliciently greater than the diameter of the positioning member 11 for a purpose which will be directly explained. t

The condenser rotors, together with the positioning member I1 and itsassociated levers l6 and 85 are moved back toward a fully operative position by the same type of spring 13 as shown in Figures .1 and 2. By fully operative position)? 'I mean that the tuning element such as the rotor of a condenser is in an allinf or allou position with respect to the stator. The spring I3 is preferably mounted on the left-hand end of the structure shown in Figures 6 and '7 and is therefore not shown in these figures.

In. order to adjust the, position of the slidable bars 20, each slide is provided with an adjusting rod 64 which is preferably permanently fixed in position in engagement" with the head 28 of the adjusting screw 21 and extends through the cabinet of the radio set, terminating at. that point in an adjusting knob or equivalent, so that any slide member may be adjusted or tuned iorany desired station without having to get into the interior of the cabinet.

Referring now to the operation of the struc ture shown in Figures 1 "to 5, which is diagrammatically illustrated in Figure 8, a. push-button structure '65, that may be located on the cabinet of the set or at some place remote therefrom, or in multiple relation, serves to close a circuit, which will be readily perceived, from a source of current supply 8 by way or the connecting rack 44 through the stop electromagnet 4|, the dectromagnet 46 and the cooperating contact 5| and the electromagnet I10 of the solenoid structure. The armature 8 of the solenoid is immediately moved to its full extent, which is at least 180 degrees, thereby moving the rotors 5 and 6 to their all-out or zero capacity position, at which point or directly prior thereto, the outer edges of the rotor plates engage the lever 53, causing it to move the spring 50 very quickly so that the contact 52 is brought into engagement with the contact on the spring 50, thereby cutting out the solenoid electromagnet, but still maintaining a circuit through the stop magnet 4| and the holding electromagnet 46.

This will hold the spring contact member 50 in this position, although the rotor, together with the solenoid armature, will start to move toward the all-in or full capacity position; but when the stop electromagnet 4| is energized as just explained, the stop lever 32 is moved into stopping position, at which particular time the positioning red I! has been moved with the rotor to the position indicated by the dotted circle a, so that when the rotor with the positioning member starts its return movement, the positioning member [1 will encounter the end 35 of the stop lever 32 at some point as indicated by the dotted circle I), this being the position for which a particular sliding member has been adjusted for a given station.

As has heretofore been explained, the pressure of the positioning member I! against the end surface '35 of the stop lever 32 is sufficient to hold the stop member in its stopping position. However, when the button of another station is pushed, the armature 8 and connected parts, including the positioning member, will be moved back to the position indicated by the dotted circle a and this releases the setting lever 32 which is moved back to normal position by its spring 36 (see Figure 3). At the same time the stop lever 32 is moved to the dotted position, the point 38 engages the member 39 and closes a circuit through the lamp L as will be observed without ,further description. When the series of buttons 65, one for each station, is mounted on the side of the cabinet, I prefer to use a construction in which the lamp L is mounted within the button and the button plunger 66 is made of a lighttransmitting material that will transmit a light through the button, so that the operator will know that the corresponding positioning member has been moved to stop position.

In Figure 9 the holding electromagnet 46 is provided with a plunger 61, just the upper end of which is shown in Figure 6, and which is adapted to be engaged by an arm or trigger member 68 carried by the solenoid armature 8 when the armature is moved to substantially its full extent (a corresponding trigger member 68' is shown connected to the toothed segment 16 when it is desired to use an electromagnetic structure 46 as shown in Figure 9). This moves the spring contact member '69 to open contacts 10 and thereby a circuit through the solenoid winding I0. At the same time, it closes contacts H thereby energizing the winding 46 which holds the plunger 67 in its actuated position.

In addition, when a push button 65 is operated, a circuit is completed through an electromagnet 12 having a movable armature or plunger 13 that closes contacts 14, completing a circuit by way of conductors 15 around the voice coil of the loud speaker. This prevents the loud speaker .from picking up stations as the rotor or movable member of the tuning structure moves from full capacity position to zero capacity position, as it does in the operation of this structure, it being understood that the push-button structure 55 is operated sufficiently long to allow these operations to take place, the time being relatively small.

Another means of eliminating noises in the loud speaker during a tuning operation isshown in'Figure 6a wherein, normally, the screw 81 and the contact member 88 are in engagement and when these contacts are closed, the antenna circuit is grounded since a wire runs from the spring contact 88 to the lead-in portionof the antenna, while the screw on the lever 85 is grounded through the framework." When the positioning member I! is in idle position; i. e., all slide members with their stop-members in idle position, the spring 9| holds the screw 8'! and spring contact 88 closed withla clearance between the-member ll and'the forked arm d, and the antenna, will be short-circuited. 1

When a button is pushed for tuning in a circuit, both'the levers F6 and 85 are moved simultaneously, it being understood that the tension of the spring 9! is sufiicient to hold the auxiliary arm 85 in the position'heretofore described. -As soon, however,- as the positioning member I! engages a stop 32 on its slide 20, it is held from further movement, but the main return spring I3 for the solenoid is strong enough to overcome the tension of the spring 9|, and the lever 16 is moved. slightly forward so that the contact between the screw 81 and spring contact 88 is opened and allows the-antenna to come into circuit. It is to be understood that the action of the solenoid is extremely rapid and the stop is very abrupt. The'lever 16 therefore has forked arms 0 and d 'which straddle the positioning member 11 to stop any superfluous movement and remove the shock from the contacts 81 and 88.

A very quick push on any button will start energization of the solenoid H), the movement of which starts movement of-the positioning member I! that releases the stop member or latch 32 that may have been previously used for holding it, However, since the electromagnet 4| is energized simultaneously with the solenoid of the electromagnet, the stop member would be moved to a stop position, provided the positioning'member hasbeen sufliciently moved to allow the stop member to move to its full stop position; but as soon as the push button is released, thestop member will move to fully released position more quickly than the solenoid armature will carry the positioning member back to its idle position. Just before the positioning member I! reaches its fully idle position, it engages the end of an insulating strip 93 (see Figures 7 and 8) that moves the spring member 94 and its contact 95, thereby breaking a circuit through a contact 96 in the current supply going to the power pack, including the power transformer, tubes, etc., but .does not disturb the circuit going to the buttons 65 and parts directly associated therewith. Since, by my construction, the movable member of the tuning structure is held in tuning position by pressure applied to th'e positioning member by the return spring means I 3, a receiving set is not susceptible to noises caused by changes in the tuning circuit due to vibrations such as might be caused by the passage of a heavy truck or the like.

The reason for the locking electromagnet 46 is to remove the relatively heavy current from the solenoid winding I o as well as from the winding :ofthe electromagnet. ll as this current has to .be of considerable strength in order to quickly operate the solenoid armature. This arrangement of the solenoid. construction and-lock-out coil is broadly. claimed in.my application, Serial No. 499,328, filed August 20, 1943, and hence will not be described further in detail herein.

While I have shown an arrangement in which the rotor of the condenser is moved through 180 degrees, I may gear the solenoid armature .so as to turn the rotor through other angles;.e..g., or'90 degrees.

Furthermore, whil I have shown the tuning element as being normally in an all-in position for movement to an "all-out position and then to tuning position,-the reverse might be accomplished by reversing the solenoid and its operation, but where-.as is the practicethe rotor plates of the tuning condensers are shaped to follow a straight line frequency or a-logarithmic or some other curve wherein the rotor plates are mounted considerably off center, the overhanging Weight of. the rotors, would be opposed to the spring which holds the positioning member I! against a'stop member. Therefore, .I...prefer to use the arrangement as illustrated, although certain of the claims herein cover both arrangements by using the term two fully-operative positions/f Also, while vI have shown two waysv of apply-. ing my invention to a misses, the tuning condenser may be placed anywhere in the set and other arrangementsoij parts. and details may be made Without departing fromthe spirit of my invention or the scope oftheappended claims. I have described two ways of muting the loud speaker. and other means'may- .be. controlled f,by the constructiondescribed. ,In the claims, where I. have referred to, a radio set. .havinga loud speaker, this means 'that the. speaker may be built into the set. or located remotely therefrom, the idea being that every radio receiving set must have a loud speaker. or the equivalent whereby the signals may be received,

WhatIclaimis:v 1. In a tuning apparatusfor a radio set having a loud speaker including, a frame carrying a condenser structure having. at least one stator and rotor unitga .primary electromagnetj supported by the frame and having, a circular type of armature mounted .to rotate, when excited, the said rotor unit from full-capacity to fullzero capacity position on each excitation of the electro-magnet, a positioning member for said rotor also mounted to be moved with the rotor unit to its full movement in one direction by said armature, and a plurality of members slidably mounted in said frame, each of said members having a stoplever adapted to engage said positioning member, and an adjusting means to move the member to a desired position in the frame, whereby the positioning member may be stopped on its return movement at a predetermined tuning position, a stop electro-magnet carried on said member for moving the stop lever to stopping position when energized with the primary electro-magnet so asto stop the positioning member and rotor-at, said predetermined position on deenergization of the primary electro-magnet, and means for returning at least the rotor and positioning member to said stop or tuning posiion. v p ,l '2. In a tuning apparatus for a-radio sethaving a loud speaker, including a frame-carrying a condenser structure having at least one stator and rotor unit, a solenoidtype of electro-magnet supported by the frame and having an armately shaped armature which has a rotary movement of at least 180 degrees, said armature and rotor having a common shaft, a positioning member for the rotor mounted to be moved by said shaft, a plurality of members slidably mounted in said frame with means for adjusting their position in the frame, each of said members having a stop lever pivotally mounted thereon and extending toward said positioning member, a stop electro-magnet carried on said member in a position to .move, when energized, said lever so its free end will be moved into the path of movement of said positioning member, so that when the solenoid and stop electro-magnets are energized preferably substantially simultaneously, the, said armature, rotor and positioning member are moved to what corresponds to the zero capacity of the condenser, means for deenergizing the solenoid as it reaches the end of said zero position, means for moving the armature, rotor and positioning member toward full-capacity position when the solenoid is deenergized, means for keeping the stop electromagnet energized long enough to hold the said lever to stop at least the positioning member and rotor on their return movement in a predetermined tuning position as determined by said slidably mounted member and its stop lever.

B. In a tuning apparatus for a radio set having a loud speaker including a frame carrying a condenser structure having at least one stator and rotor unit, a solenoid type of electromagnet supported by the frame and having an arcuately shaped armature which has a rotary movement of at least 180 degrees, said armature and rotor having a common shaft, a positioning member for the rotor mounted to be moved by said shaft, a plurality of members slidably mounted in said frame with means for adjusting their position in the frame, each of said members having a stop lever pivotally mounted thereon and extending toward said positioning member, a stop electro-magnet carried on said member in a position to move, when energized, said lever so its free end will be moved into the path of movement of said positioning member, so that when the solenoid and stop electro-magnets are energized preferably substantially simultaneously, the said armature, rotor and positioning member are moved to what corresponds to the zero capacity of the condenser, means for deenergizing the solenoid as its armature reaches the end of said zero position, means acting on the armature shaft to move it along with the rotor and positioning member toward their initial starting position, a supplemental electromagnet acting through locking contacts tokeep the stop electromagnet acting through locking contacts to keep the stop electromagnet energized to thereby hold said lever in stop position to engage and stop the positioning memher and rotor in a predetermined position on their return. movement.

4. In a tuning apparatus as set forth in claim 3-, further defined in that the supplemental electromagnet is brought into its locking position primarily by the movement of said solenoid armature at substantially the end of its-power stroke. 7 t 7 I 5. In a tuning apparatus as set forth in claim 3, further definedin that the supplemental elec- 3,, further defined in that the supplemental electromagnet is connected in series with the solenoid and stop electromagnet, the supplemental electromagnet having an armature controlling contacts in the solenoid circuit as well as said locking contacts, and means for acting on said armature at the end of the initial movement as set forth for moving it into a position whereby it opens the solenoid circuit contact and closes said locking contacts.

Z. In a tuning apparatus asset forth in claim 3, further defined in that the supplemental electromagnet is connected in series with the solenoid and stop electromagnet, the supplemental electromagnet having an armature controlling contacts in the solenoid circuit as well as, said locking contacts, and a lever moved by the condenser rotor as it reaches zero capacity during the initial movement of the. solenoid armature for acting on said armature at the end of the initial movement as set forth for moving it into a position whereby it opens the solenoid circuit contact and closes said locking contacts.

8. In a tuning apparatus as set forth in claim 3, further defined in that the solenoid deenergizing means is actuated bymovement of its own armature.

9. In a tuning apparatus for a radio set having a loud speake including a frame carrying a condenser structure having at least one stator and rotor unit, a solenoid type of electromagnet supported by the frame and having an arcuately shaped armature which has a rotary movement of at least degrees, said armature and rotor having a common shaft, a positioning member for the rotor mounted to be moved by said shaft, a plurality of members slidably mounted in said frame with means for adjusting their position in the frame, each of said members having a stop lever pivotally mounted thereon and extendingv toward said positioning member, a stop electromagnet carried on said member in a position to move, when energized, said lever so its free end 'will be moved into the path of movement ofsaid positioning member, so that when the solenoid and stop electromagnets are energized preferably substantially simultaneously, the said armature, rotor and positioning member are moved to what corresponds to the zero capacity of the condenser, means for deenergizing the solenoid as its armature reaches the end of said zero position, means acting on the armature shaft to move it along with the rotor and positioning member toward their initial starting position, a supplemental electromagnet acting through locking contacts to keep the stop electromagnet energized to thereby hold said lever in stop posi tion to engage and stop the positioning memher and rotor in a predetermined position on their return movement, and a relay brought into operation substantially simultaneously with the energization of the stop electromagnet, said relay having contacts for closing a circuit for shorting preferably the voice coil of the loud speaker of the set.

10. In a tuning apparatus as set forth in claim 1, further defined in that said adjusting means includes a screw turnable in a part of the frame without longitudinal movement, the slidable memher having a threaded lug to receive the threads screw between the lug and the said frame part.

11. In a tuning apparatus as set forth in claim 1, further defined in that said adjusting means includes a screw turnable in a part of the frame without longitudinal movement, the slidable member having a threaded lug to receive the threads of the screw whereby the said member is moved on turning the screw, and a spring carried by the screw between the lug and the said frame part, and a rod preferably in permanent engagement with the head of the screw, the rod extending to a convenient position for adjustment purposes such as to the exterior of the radio set.

12. For a radio receiving set; a tuning structure having a rotatable tuning member normally positioned in full all-in tuning position, means for moving said tuning member to full all-out tuning position and then immediately automatically releasing it, means for then moving the tuning member toward the all-in position, and means for stopping the tuning member at a predetermined tuning position, said last mentioned means including an adjustable presetting structure carrying a stop member andan electro-magnet for actuating the stop member, and a push button apart from said structure for closing a circuit through said electro-magnet.

13. For a radio receiving set; a tuning structure having a movable tuning member having two fully-operative positions, means for moving said tuning member from any position it may be in to one of its two fully operative positions and then automatically releasing it, means for then automatically moving the tuning member toward the other of said two positions, an adjustable presetting structure carrying cooperative means including a stop member and. electrically actuating means therefor, to move thestop member into stopping position for stopping the tuning member at a predetermined tuning position as defined by said presetting structure. l

14. For a radio receiving set; a tuningstructure having a rotatable tuning member having two fully operative positions, a solenoid type'of electromagnet having a circular type armature operatively connected to said rotatable tuning member and operating to move said member from any position which it may be in to one of its two fully operative positions, means for releasin said armature when said one position is reached, means for moving said armature and member toward the other of said two positions, and means for stopping said member on its return movement in a predetermined position.

15. For a radio receiving set; a tuning structure having a movable tuning member having two fully operative positions, electromagnetic means for moving said member all the way from any tuning position it may be in to one of its two fully operative positions, means for then automatically releasing it, means for returning-said membertoward the other of said two tuning positions, and means for stopping it on its return movement in a predetermined tuning position, said last'mentioned means including an adjustable presetting structure carrying a stop member and an electro-magnet for moving the stop member into stopping position, and a simple push button mounted apart from said presetting structure for closing a circuit through the stop electro-magnet.

16. For a radio receiving set; a tuning structure having a movabletuning member having two fully operative positions, electromagnetic means for moving said member all'the way from any tuning position it'may be in toone of its two fully operative positions, means controlled by said electromagnetic means for releasing itself and said movable tuning member when the said one position is reached, means for returning said member toward the other of said two tuning psitions, a presetting'station selecting structure carrying-a stop member and an eleotromagnet for moving the stop member into position for stopping said movable tuning member on its return movement in a predetermined tuning position and a push button mounted apart from said presetting'structure for closing a circuit through the stop electro-magnet.

17. In a tuning apparatus for a radio set including a frame, members slidably mounted in the frame, each of said members having means for reducing to a minimum wobble particularly in a direction at right angles to its direction of motion, a stop member carried by said slidable member, an electromagnet also carried by said slidable member for moving'said stop member into stopping position, a positioning member mounted in the frame, a tuning member forming part of a tuning structure movably carried by the frame and operatively connected to the positioning member, a solenoid electromagnet having an armature operatively connected to said tuning member and thepositioning member for moving both of said members to an all-out tuning position, means for releasing them when the all-out position is reached, and means for moving at least the tuning member toward an all-in posi tion, said electromagnets on the slidable member acting to move the stop member into position to stop the positioning member in a predetermined position as defined by the position of said slidable member. I J

18. A tuning apparatus as set forth inrclaim 17, further defined in that the slidable member has a threaded lug to receive a screw, the head' of which is positioned against a frame memberv so as to prevent longitudinal movement of the screw, and a compression spring carried by the screw be tween said lug and said frame member. V

19. A tuning apparatus as set forth in claim 17, further defined in that said means for reducing wobble comprises a finger located at that end of the slidable member at which the electromagnet is positioned and adapted to resiliently engage a frame support part, while the other end of said slidable member is divided into two portions which are adapted to resiliently engage another frame support part.

20. In a tuning apparatus for a radio set including a frame, a plurality of members, one to any desired radio station, mounted with resilient engagement between spaced frame parts withadjustable means for sliding saidmembers onsaid parts, each member having a stop lever pivoted thereon and an electromagnet for moving 'sa'id lever to stop position, a positioning member oscillatably carried in the frame in a position -to be engaged by said stop member, a rotatable tuning member mechanically connected to said-positioning member, a solenoid type of elec'tromagnet having a circular type armature capable-of turnin through at least degrees with the-armature connected to said rotatable tuning member and the positioning member, the armature moving to its fully'operative position whenever its solenoid is energized, means for deenergizing the solenoid at the end of its working strokegmeans for-mov ing the armature, tuningmemberand-positioning member toward full tuning position until stopped by a stop lever set in stopping position by its electromagnet whenever the solenoid is energized.

21. In a tuning apparatus for a radio set including a frame, a plurality of members, one to any desired radio station, mounted with resilient engagement between spaced frame parts with adjustable means for sliding said members on said parts, each member having a stop lever pivoted thereon and means for moving said lever to stop position, a positioning member oscillatably carried in the frame in a position to be engaged by said stop member, a rotatable tuning member mechanically connected to said positioning member, an electromagnet having an armature capable of turning through at least 180 degrees with the armature operatively connected to said rotatable tuning member and the positioning memher, the armature, when its electromagnet is energized, acting to move the said parts connected thereto to a non-tuning position against returning means, means for then deenergizing the said electromagnet and allowing said returning means to move the said connected parts toward a tuning position as defined by said stop lever.

22. In a tuning apparatus fOr a radio set, a tuning structure including a movable member having two fully operative positions, means including a solenoid type of electromagnet having a circular type armature for moving said member to one of its fully operative positions and then automatically releasing itself and further means for moving said movable member toward the other of said two positions, and means for automatically stopping it at the tuning position desired, said stopping means including a tuning slide structure carrying a stop member and an electro-magnet for moving the stop member to stopping position, and a push button for closing a circuit through the electro -magnet.

23. In a tuning apparatus for a radio set, a tuning structure including a movable member having two fully operative positions, means for moving said member to one of its fully operative positions and then moving it toward the other of said two positions, a positioning member and a stop device therefor moved simultaneously with said movable tuning member, the stop device being in the path of the return movement of the positioning member to stop it and the tuning member in a desired tuning position, and means for holding, under pressure, the positioning member against the stop device for the purpose described.

24. In a tuning structure as set forth in claim 13, further defined in that said electrically actuated means forming part of said cooperative stopping means consists of an electromagnet having a lever-type armature moved into the stopping position on energization of the electromagnet.

25. In a tuning structure as set forth in claim 13, further defined in that said electrically actuated means forming part of said cooperative stopping means consists of an electromagnet having substantially a closed magnetic circuit comprising a lever-type armature with a part moved into close relation to the core on energization of the electromagnet, and another part moved simultaneously into the stopping position.

26. In a tuning structure as set forth in claim 13, further defined in that said electrically actuated means forming part of said cooperative stopping means consists of an electromagnet having substantially a closed magnetic circuit comprising a lever-type armature with a part moved into close relation to the core on energization of the electromagnet, and another part moved simultaneously into the stopping position, the said lever-type armature part acting with the other parts of the magnetic circuit of the electromagnet, after it has been energized, to retain residual magnetism sufficient to hold the lever in stopping position after the electromagnet has been deenergized.

2'7. In a tuning structure as set forth in claim 13, further defined in that said electrically actuated means forming part of said cooperative stopping means consists of an electromagnet having substantially a closed magnetic circuit comprising a lever-type armature with a part moved into close relation to the core on energization of the electromagnet, and another part moved simultaneously into the stopping position, this lastmentioned part having a formation adapted to be engaged by a positioning member comprising part of said stopping means so as to insure that any residual magnetism in the magnetic circuit, in cluding the said lever, will not interfere with the proper return of the lever to normal position after being released by the positioning member.

28. In a tuning structure as set forth in claim 13, further defined in that said electrically actuated means forming part of said cooperative stopping means consists of an electromagnet having a lever-type armature moved into the stopping position on energization of the electromagnet, the free end of the lever armature having a formation adapted to be engaged by a positioning member comprising part of said stopping means so as to form a positive stop between the two parts and insure that the lever will return to normal position when released by the positioning member.

STANLEY S. CRAMER.

CERTIFICATE OF CORRECTION.'

Pateht No. 2',589,h87. November '20,- 131 sum 3. GRAMER.

It is hereby certified error appears 'i'nizhe printed epecificetion of the-above x'mmbe'ret} patent requiring correction as follbwe': Page 5, firet' column, linee 62 and 65, elaign 5, strike eutthe words Faeting threugh lockcontacts to keep the stop electromagnet"; end that the said Letters Put em: should he read w dth this correction therein that the same may confer-m to the recorder the case if: the Patent Office;

Signed "and sealed "this" 5th day of February, A. D. 191M:-

Leslie Frazer -U First Assistant; Cqmnisioner pf Barents. 

